1. Field of the Invention
The present invention relates to a radiation imaging apparatus, a method for manufacturing the same, and a radiation imaging system.
2. Description of the Related Art
A radiation image can be generated by an apparatus including a scintillator layer which converts radiation into light and a sensor array having a plurality of sensors which perform photoelectric conversion. Japanese Patent Laid-Open No. 2003-262673 discloses a technique of adding an activator agent to a scintillator layer of columnar crystals so as to cancel out the nonuniform distribution of luminance efficiency of the layer due to the nonuniform column diameters of the crystals. According to Japanese Patent Laid-Open No. 2003-262673, it is possible to form a scintillator layer having a uniform distribution of luminance efficiency.
A radiation imaging apparatus D as a reference example will be described with reference to FIGS. 1A and 1B. As exemplarily shown in FIG. 1A, the radiation imaging apparatus D can include a sensor array 20 including a plurality of sensors 21 designed to perform photoelectric conversion and arranged on a substrate 10 in the form of an array and a scintillator layer 30 formed on the sensor array 20. Referring to FIG. 1A, the arrows schematically show light generated in a region immediately above each sensor 21 in the scintillator layer 30. FIG. 1B shows the distribution of the amounts of light received by the respective sensors 21 when the radiation imaging apparatus D is irradiated with uniform radiation. An abscissa x represents an axis taken along the direction from an end portion of the sensor array 20 as an origin to the center of the sensor array 20. An ordinate y represents the amounts of light received by the sensors 21 corresponding to the abscissa x. Although the amounts of light generated in the regions immediately above the respective sensors 21 in the scintillator layer 30 are uniform, the amounts of light entering the sensors 21 at the end portion are small. That is, although the scintillator layer 30 has a uniform luminance efficiency, the amounts of light received by the respective sensors 21 are nonuniform. That is, the sensitivity of the radiation imaging apparatus D is nonuniform with respect to radiation.